SAN FRANCISCO (Reuters) - California Governor Jerry Brown on Monday laid out an ambitious plan for 50 percent of the state's electricity to be generated by renewable resources over the next 15 years and to cut petroleum usage by drivers.

Brown, who was sworn in for an unprecedented fourth term, said he would also seek to double the energy efficiency of existing buildings and make heating fuels cleaner.

"I envision a wide range of initiatives: more distributed power, expanded rooftop solar, micro-grids, an energy imbalance market, battery storage, the full integration of information technology and electrical distribution and millions of electric and low-carbon vehicles," Brown said in his speech in Sacramento.

The state has pushed to implement far-reaching climate change policies, including its landmark AB 32 law aimed at reducing carbon pollution back to 1990 levels by 2020. Brown said California was on track to meet its goal of generating one-third of the state's electricity through renewable energy within the next five years.

The governor's new initiative could be a boon for green energy companies, such as manufacturers of electric vehicles and those looking to build utility-scale solar projects or upgrade the state's aging electric grid.

SolarCity Corp, the largest U.S. residential solar panel installer, and Vivint Solar Inc are already big players in California. NRG Energy Inc , a top competitor on the East Coast, announced in November that it aimed to open new offices in California.

A trio of companies including Duke Energy Corp in September proposed an $8 billion green energy initiative for Los Angeles.

Since 2013 California's cap-and-trade program has raised nearly $1 billion from companies to offset their carbon emissions. The money could increase significantly as the program expands this year to cover distributors of transportation fuel like gasoline and diesel and home heating fuels like natural gas.